Apps script: map not returning expected value to array

Question

I have an array of objects that looks like:

var objArray = [
  {
    " #": "4596",
    " E": "Yes",
    " Date": "06/12/20",
    " County": "Los Angeles County",
    " State": "California",
    " Acres": "2.49",
    " Eager": "Low",
  },
  {
    " #": "4588",
    " E": "Yes",
    " Date": "06/11/20",
    " County": "Towns County",
    " State": "Georgia",
    " Acres": "3.00",
    " Eager": "High",
  },
  ....
];

I'm trying to put together an array of the indexes ('#');

So far I have:

let indexes = objArray.forEach(function (rowObj) {
  Object.keys(rowObj).map(function (key) {
    if (key.includes("#")) {
      var v = rowObj[key];
      Logger.log(v); // abc
      return v;
    }
  });
});

Logger.log(indexes); // abc

output:

[20-06-13 20:43:33:320 EDT] 4547
[20-06-13 20:43:33:324 EDT] 4546
[20-06-13 20:43:33:329 EDT] 4545
[20-06-13 20:43:33:450 EDT] 4543
[20-06-13 20:43:33:453 EDT] 4542
[20-06-13 20:43:33:456 EDT] 4540
[20-06-13 20:43:33:459 EDT] 4538

This is producing:

[20-06-13 20:43:33:462 EDT] null

What am I doing wrong?

0Valt · Accepted Answer · 2020-06-14 01:27:36Z

6

As a supplementary answer:

You can do this even simpler and faster.

const values = [
  { " #": "4596", " E": "Yes"},
  { " #": "4597", " E": "No"},
  { " #": "4598", " E": "Maybe"},
]

const indices = values.map(({ " #" : id }) => id);

console.log(indices);

Please, note that callback to map() method should be deterministic to acheive a consistent result.

Actual problem

Check the documentation on forEach() method - it is intended for producing side-effects and therefore returns void (literally no value), hence the last Logger.log(indexes); issue.

Useful links

map() method reference
Arrow functions guide
forEach() method reference

edited Jun 14, 2020 at 1:27

answered Jun 14, 2020 at 1:16

0Valt

10.5k9 gold badges41 silver badges66 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user1592380 Over a year ago

Its a great idea, but when I run it in apps script I get: [null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null]

0Valt Over a year ago

Does the # comes prefixed with whitespace in your real code? Could tou show how you implemented the suggestion?

0Valt Over a year ago

You have to make sure the following is true: 1. map is called directly on the array of objects (objArray). 2. The " #" key consists exactly of whitespace and hash chars. 3. V8 runtime is enabled (the same goes for Mario's answer, btw)

Mario · Accepted Answer · 2020-06-14 15:43:09Z

3

If the key you are looking for is always # and if it is present in all objects you could simplify the logic using reduce. Please look at the following example

const objArray = [
  {
    " #": "4596",
    " E": "Yes",
    " Date": "06/12/20",
    " County": "Los Angeles County",
    " State": "California",
    " Acres": "2.49",
    " Eager": "Low",
  },
  {
    " #": "4588",
    " E": "Yes",
    " Date": "06/11/20",
    " County": "Towns County",
    " State": "Georgia",
    " Acres": "3.00",
    " Eager": "High",
  },
];

const output = objArray.reduce(
  (previousValue, currentValue) => [...previousValue, currentValue[" #"]],
  []
);

console.log(output)

Update 0

Reduce you use it when you need to compact the content of an array, its operation is very similar to filter and map in that they use a callback function that is executed in each entry of the array, the difference is that it reduces takes as initialValue argument which you update in each iteration.

For example, this is the same version without the shortcuts that allow you to use the arrow functions, previousValue corresponds to the initialValue, and currentValue to the object in each iteration. So in each iteration you spread the content of previousValue and get and attach the value of the # property of currentValue

Run the example so you can see the values of the previousValue in each iteration

const objArray = [
  {
    " #": "4596",
    " E": "Yes",
    " Date": "06/12/20",
    " County": "Los Angeles County",
    " State": "California",
    " Acres": "2.49",
    " Eager": "Low",
  },
  {
    " #": "4588",
    " E": "Yes",
    " Date": "06/11/20",
    " County": "Towns County",
    " State": "Georgia",
    " Acres": "3.00",
    " Eager": "High",
  },
];

const output = objArray.reduce((previousValue, currentValue) => {
  console.log(previousValue);
  previousValue = [...previousValue, currentValue[" #"]];

  return previousValue;
}, []);

console.log(output);

This post was the first I read about reduce, it explains the concept in a practical and simple way. I recommend your reading. Cheers

edited Jun 14, 2020 at 15:43

answered Jun 14, 2020 at 1:25

Mario

5,0044 gold badges42 silver badges65 bronze badges

4 Comments

user1592380 Over a year ago

Thank you - I'm fairly new to js and reduce. Would you mind explaining what you've done here?

user1592380 Over a year ago

I apologize , its a great explanation. I'm familiar and have used reduce before, but at a beginning level as in your explanation. I'm less clear about the function you are using - (previousValue, currentValue) => [...previousValue, currentValue[" #"]] - Is previous value the accumulator?

Mario Over a year ago

I understand. Yes previousValue is the accumulator. About [...previousValue, currentValue[" #"]] I am using spread syntax to expand the current accumulator in a new array plus the value of currentValue in property ` #`

0Valt Over a year ago

@LDN - the [...sourceArray, value] is just a more concise way to right sourceArray.concat([ value ]) since ES6 came around (see spread in array literas)

Cooper · Accepted Answer · 2020-06-14 01:11:44Z

2

I think your return in the middle of the loop was the problem. Other than that it's okay works fine.

This works for me:

function functest() {
  var objArray =[{" #":"4596"," E":"Yes"," Date":"06/12/20"," County":"Los Angeles County"," State":"California"," Acres":"2.49"," Eager":"Low"},
                 {" #":"4588"," E":"Yes"," Date":"06/11/20"," County":"Towns County"," State":"Georgia"," Acres":"3.00"," Eager":"High"},
                 {" #":"4596"," E":"Yes"," Date":"06/12/20"," County":"Los Angeles County"," State":"California"," Acres":"2.49"," Eager":"Low"},
                 {" #":"4588"," E":"Yes"," Date":"06/11/20"," County":"Towns County"," State":"Georgia"," Acres":"3.00"," Eager":"High"},
                 {" #":"4596"," E":"Yes"," Date":"06/12/20"," County":"Los Angeles County"," State":"California"," Acres":"2.49"," Eager":"Low"},
                 {" #":"4588"," E":"Yes"," Date":"06/11/20"," County":"Towns County"," State":"Georgia"," Acres":"3.00"," Eager":"High"},
                 {" #":"4596"," E":"Yes"," Date":"06/12/20"," County":"Los Angeles County"," State":"California"," Acres":"2.49"," Eager":"Low"},
                 {" #":"4588"," E":"Yes"," Date":"06/11/20"," County":"Towns County"," State":"Georgia"," Acres":"3.00"," Eager":"High"}];
  var oA=[];
  let indexes=objArray.forEach(function(rowObj) {
    Object.keys(rowObj).map(function(key) {
      if (key.includes('#') ) {
        var v = rowObj[key];
        oA.push(v);
      }
    });
  });
  Logger.log(oA);
}//[4596, 4588, 4596, 4588, 4596, 4588, 4596, 4588]

edited Jun 14, 2020 at 1:11

answered Jun 14, 2020 at 1:04

Cooper

64.2k7 gold badges28 silver badges65 bronze badges

1 Comment

Cooper Over a year ago

I find this a lot quicker to use to view results: SpreadsheetApp.getUi().showModalDialog(HtmlService.createHtmlOutput(oA.join('<br />')), "Display Results");

Collectives™ on Stack Overflow

Apps script: map not returning expected value to array

3 Answers 3

3 Comments

4 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

4 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related